1. Field of the Invention
This invention relates to a rotational position detector useful for the electronic control of an internal combustion engine. In addition, a device is disclosed for detecting the rotational angular position of a rotating body for engine control, employing a control system for processing pulses which are generated by means of a plural number of detectable portions provided around the circumference of a rotating body like the engine crankshaft and a sensor located adjacent to the rotating body. Further, a device is disclosed for detecting a reference position on a rotating body, wherein a reference position of pulses representing angular information is given by a nonuniformly spaced portion for a signal generating means of a rotary body of a crank angle sensor or the like to be used as a vehicle control unit, for electrically detecting the rotational angle or the number of revolutions of the rotary body on the basis of the reference position.
2. Description of Background Art
For controlling operations of an internal combustion engine by electronic control units such as, for example, a fuel injection control unit or an ignition timing control unit, it is necessary to detect accurately the rotational position of the engine, for example, the angular position of the engine crankshaft. A rotational position detector or sensor of this sort is known, for example, from U.S. Pat. No. 4,553,426.
The conventional detector is arranged to generate pulse trains partly containing a nonuniformly spaced interval in synchronism with rotation of a rotary body, detecting a predetermined angular position of the rotary body from the condition of generated pulse trains, and upon detection producing a reference pulse separately from the pulse trains, and verifying the correctness of the reference pulses by producing a verified reference pulse when a count of pulses of a pulse train between a reference pulse and a preceding reference pulse equals a predetermined number. A conventional detector has a problem in that the detection of the rotational position lacks adaptability to high speed rotations, in addition to incapability of instantly distinguishing abnormalities in the results of detection.
Namely, when the rotation of the rotary body contains fluctuations as experienced during engine operations, complicate computations are required for generation of the reference pulses, failing to adapt the detection process to high engine speeds while taking time for performing necessary arithmetic operations.
Besides, the verification of the reference pulses, namely, the verification of the correctness of the pulse count of the pulse train necessitates operations for discrimination of the reference pulses and collation of the pulse counts of the pulse trains, which cause a further delay before generation of the verified reference pulses and impose adverse effects in a greater degree at higher engine speeds.
Further, the correctness of the detected reference positions is verified only on occurrence of the reference pulses so that it is difficult to detect promptly an error which might occur to the pulse count of the pulse train between the two reference pulses, namely, to the detected rotational position, resulting in a delay in discriminating abnormalities which take place during the detection process.
Heretofore, there have been in use various vehicle engine control systems, which invariably have a difficulty in performing required arithmetic operations in response to quick variations since the period of the arithmetic operation becomes very short at high speed rotations.
In order to eliminate this problem, Japanese Patent Publication No. 61-33984 discloses a system, including, as shown in FIGS. 21 and 22, three projections 2B protruded at uniform intervals of 120 degrees from the circumference of a disk 1B which is mounted on an engine crankshaft 2B. The projections 2B are formed of a magnetic material to cooperate with an electromagnetic pickup 3B having a coil winding around a magnet and located closely to the circumference of the disk 1B which carries the projections 2B. This electromagnetic pickup 3B is connected to a shaper 4B to induce a reference signal in the electromagnetic pickup at a time point when each one of the projections 2B on the disk 1B is passed across the front side of the electromagnetic pickup 3B, amplifying and shaping the reference signal to produce a reference pulse signal. A processor 5B is connected to the output of the shaper 4B to supply thereto the reference pulse signal as an input for performing arithmetic operations software-wise. In addition, various sensors 6B are also connected to the input of the processor to provide other controlling input signals. A presettable downcounter 7B and an R-S flip-flop 8B are connected in parallel to the output of the processor 5B, connecting the output of the presettable downcounter 7B to the input terminal (R) of the R-S flip-flop 8B, while connecting a clock pulse generator 9B of a predetermined frequency to the input of the presettable downcounter 7B. Connected to the output of the R-S flip-flop 8B is an amplifier 10B which has its output terminal connected to an electromagnetic injection valve 11B.
With this system, reference signals are produced at the output terminal A of the shaper 4B in synchronism with the rotation of the engine crankshaft. The reference pulse signal is applied to an interrupt request terminal INT of the processor 5B, so that, as shown in the flowchart of FIG. 22, the processor 5B receives an interrupt request each time a reference pulse signal is applied (Step 12B), reading in the information of a rotational speed (the number of engine revolutions) sensor among a group of sensors B to check if the rotational speed is higher than a predetermined speed, for example, higher than 3000 r.p.m. (Step 13B), setting "0" for the initial value i to be used in this processing if lower than the predetermined speed (3000 r.p.m.) (Step 14B), followed by executing part of the arithmetic operation for computing the fuel injection period (Step 15B), next making a check to see if the initial value i is "0" (Step 16B), advancing in the direction of YES since the initial value i was set to zero at Step 14B, setting the addressing value to w1 and specifying that part of the arithmetic operation was executed at Step 15B. Step 17B executes the remainder of the arithmetic operation performed at Step 15B. Step 18B sends the results of the arithmetic operation as an input to the presettable downcounter (Step 19B), and ending the interrupt processing (Step 20B).
On the other hand, if the engine revolution is higher then the predetermined speed (3000 r.p.m), the sequence is branched from Step 13B, setting the initial value i to "1" and jumping to Step 15B if the addressing value ADR was set to w1 and to Step 17B if the addressing value ADR was set to w2 (Step 21B). Further, when the initial value i is "1", the processing line is branched from Step 16B, setting the addressing value to w2 and specifying that the next arithmetic operation is processed at Step 18B (Step 22).
At a time point when the output of the processor 5B is received by the presettable downcounter 7B, the R-S flip-flop 8B is set, and the downcounter 7B immediately initiates down counting in response to clock pulses from the generator 9B, producing a borrow signal at a time point when the memory content becomes zero to reset the R-S flip-flop 8B. Therefore, the R-S flip-flop produces a set output C of a time width proportional to the computed value provided as an output of the processor 5B. This set output C of the R-S flip-flop 8B is amplified by the amplifier 10B and applied to the electromagnetic valve 11B as an open valve signal.
Heretofore, there have been known engine crankshaft angle detectors for operating the ignition and fuel injection units of an engine, which are generally arranged to discriminate grooves or projections provided on a circumferential portion of a disk-like rotary body by means of a closely located sensor.
As discussed above, U.S. Pat. No. 4,553,426 discloses a device of this sort, in which grooves or projections are provided on the circumference of a rotary body at uniform intervals except for a nonuniformly spaced portion.
More specifically, as shown in FIG. 40, rectangular projections 3C are provided at uniform intervals around the circumference of a rotary body 2C to serve as an engine control system 1C, omitting the rectangular projection in one position to form a nonuniformly spaced interval 4C. A sensor 6C is located in a position adjacent to the rotary body 2C, with a sensitive side of the sensor positioned toward the rectangular projections 3C. Connected to the output of the sensor 6C through a connection terminal A is a buffer, synchronizer and shaper circuit 7C, and connected to the output of the buffer, synchronizer and shaper circuit 7C through a connection terminal B are a pulse lack sensor 8C for detecting the nonuniformly spaced portion 4C, a verification circuit 9C which is also connected through a connection terminal C at the output of the pulse lack sensor 8C, and an engine control circuit 10C for wiring output line 10a to control units on the engine. In the verification circuit 9C, the input of a counter 11C is connected to the output of the buffer, synchronizer and shaper circuit 7C through the connecting terminal B, with output terminals Q.sub. 1, Q.sub.2 and Q.sub.6 of the counter 11C connected to the input terminals of AND gate 12C. The output of AND gate 12C is connected through a connection terminal E to the input of another AND gate 13C. The output of AND gate 13C is connected through connection terminal F to the input of the engine control circuit 10C. Line 15C branched from the connection terminal C and line 16C branched from the connection terminal E are connected to the input of logic and delay reset circuit 14C the output of which is connected to the input of the counter 11C. Line 17C branched from the connection terminal C is connected to another input terminal of AND gate 13C. Line 18C branched from the connection terminal F is connected to the set terminal of a flip-flop circuit 19C the output of which is connected through connection terminal G to one input terminal of the engine control circuit 10C. The reset terminal of the flip-flop circuit 19C is connected through line 20C to a point between the node H which is connected at one end to a parallel circuit of condenser 21C and resistor 22C and grounded at the other end through line 23C. The node H is connected to one end of a parallel circuit of resistor 24C and rapid discharge diode 25C, with the other end connected to one terminal of a switch 27C. The other terminal of the switch 27C is connected to the anode of a power source 28C which has its cathode grounded.
A power supply line B+ is connected to the engine control circuit 10C and flip-flop circuit 19C through line 26C.
With the above-described arrangement employing a single sensor for detection of the reference position, the pulse lack detector 8C is provided on the output side of the sensor as a circuit serving exclusively for discrimination of the nonuniformly spaced portion 4C, matching the number of projections on the rotary body 2C with the number of pulses, and initializing the count of the projections each time upon detection of the nonuniformly spaced portion 4C to discriminate the reference position periodically.